The present invention relates to a switch for use in, for example, a door switch in a refrigerator, and in particular, to a switch such as a push-button switch and a rotary-lever switch which can reduce the number of parts and also achieve stable contact performances.
In general, a switch used for a domestic electric appliance, for example, a door switch installed in a domestic refrigerator, has switching functions which turns on and off a lamp in the refrigerator, and also turns on and off a cooling motor, when the door of the refrigerator is opened and closed.
The amount of protrusion of an operation unit (actuator) for the switch to be press-down operated tends to vary due to a dimensional error between the external shape of the door switch and the shape of a recessed portion of the attaching position in the refrigerator. This results in the operation unit tending to have an excessive or insufficient operation in its stroke, making it difficult to maintain switching functions of the door switch.
In order to obtain stable on-off operations without having adverse effects caused by deviations in attaching precision in the door switch, a longer operation stroke is required in the operation direction. However, at present, the application of a longer operation stroke makes the switch itself become bulky, and might cause damages to switching parts due to an over-stroke.
Depending on differences in the open-close system of the door, such as a one-side opening system and a two-side opening system, there are two types of door switches in the operation direction of the door switch. Specifically, there is a push-button type in which the switching operation is carried out by advancing or retreating in the straight line direction, and a rotary-lever type in which the switching operation is carried out while rotating. Different contact structures need to be prepared depending on the respective types.
When, upon a switching operation, the contact switching between contacts is slow, an arc tends to be caused, resulting in a defective contact. In order to prevent this defective contact, a snap action opening and closing mechanism, which quickly carries out switching between contacts, or an opening and closing mechanism having the same function, needs to be prepared.
In order to solve such a problem, a switch has been proposed in which, in cooperation with a depressing operation of a push button, a movable contact which moves in a tilted manner between a tilt position having a tilt angle of approximately 45xc2x0 with one end supported by a coil spring and a vertical position so as to switch contacts (for example, see Japanese Laid-Open Patent Application No. 11-111105).
However, such a switch needs a fixed contact and a movable contact inside thereof and an exclusively-used coil spring that allows the movable contact to return to its original position. This results in a complicated contact structure, and upon assembling the switch, handling and assembling of the coil spring having an elastic force are difficult. A number of parts and manufacturing processes are also required, resulting in a limitation to cost reduction.
Although, upon switching contacts, this structure has a sliding contact function which switches contacts with the contact portion of the movable contact sliding on the contact portion of the fixed contact while removing an oxide film, it is susceptible to great abrasion and the resulting in short service life.
In addition to these problems, when one door switch is used for turning on-off the lamp illuminating the inside of a refrigerator as well as for turning on-off the cooling motor, a single-pole double-throw switch, which has a normally-closed and normally-open contact construction that turns the switch on and off in response to opening and closing of the door, is required. However, in the case of a door switch which only turns on-off the lamp or only turns on-off the cooling motor, it is easily manufactured by using only the single-pole single-throw switch that has a normally-closed or normally-open contact construction.
However, in the case of this single-pole single-throw switch, since the switch structure is different depending on the normally-closed and normally-open contact constructions, the same housing is not used commonly, and housings corresponding to different contact structures of two types need to be prepared. For this reason, at present, a single-pole single-throw door switch, which can be switched between the normally-closed state and normally-open state by using a single-switch construction, is used as a single-pole single-throw door switch, and either of the contact constructions is selectively used depending on the use.
However, when only one of the normally-closed and normally open contact constructions is selectively used, the other contact construction on the unused side is never used, making the door switch uneconomical with the unused contact parts still assembled therein, as well as causing high costs.
For this reason, it has been proposed that the contact parts on the unused side have been preliminarily omitted. However, in this case, a space is formed in the housing after the contact parts on the unused side have been removed, with the result that the movable contact member facing the space becomes difficult to take a normal amount of shift due to an excessive tilt, etc. Consequently, the movable contact member has a positional deviation or the like, making the contact structure unbalanced, thereby resulting in susceptibility to failure and degradation in the contact performance. Therefore, this case needs the addition of a revising member such as a dummy contact to prevent the movable contact member from having the excessive tilt, and since the addition of one part causes a great increase in the manufacturing costs in mass-produced switches, there has been a strong demand for the development of switches from which the dummy contact has been eliminated.
In one embodiment of the invention, the movable contact member has two functions, including a spring function configured to elastically shift in addition to a contact function, which is provided as a single commonly-used part. The invention provides a switch having high reliability, such as a push-button switch and a rotary-lever switch, which can cut costs by reducing the number of parts, achieve a small-size device and a high assembling property, and ensure a superior contacting property by using a snap action to provide a longer service life.
In another embodiment of the present invention, a switch, which has a concave-shaped housing with one side being opened, a cover for sealing the opened face and a fixed conductive contact member and a movable contact member that are placed face to face with each other in the housing such that an operative force of operation members that are held in the housing and operated is transmitted to the movable contact member so that the movable contact member is moved and shifted to connect and separate the contacts so as to carry out a switching operation, is provided with a common fixed contact member and a fixed contact member that is different from the common fixed contact member that are placed in parallel with each other in the housing. The movable contact member, which has a tilt-movement fulcrum portion that is placed orthogonal to the parallel arranging direction of the respective fixed contact members, in a manner so as to freely tilt in the orthogonal direction, while being pressed toward the common fixed contact member side, at an intermediate position on one side member of a conductive plate spring member that is bent into a U shape, and a contact portion formed at one end of the one side member in the length direction with the tilt-movement fulcrum portion in the movable shifting direction of this one side member serving as a base point, is placed. In the arrangement a contact switching mechanism is installed which carries out a switching operation by reversing the movable contact member in a seesaw manner, based upon the operative force of the operation members that are made in contact with the movable contact member along the outer face length direction on the other side member thereof, with respect to contacting and separating processes between the contact portion of the fixed contact member and the contact portion of the movable contact member that are placed face to face with each other, with the tilt-movement fulcrum portion of the movable contact member being always in contact with the contact portion of the common fixed contact member.
The switch is applicable to a door switch of a refrigerator that turns on and off in response to the door opening and closing operations.
The housing is formed, for example, so as to have a concave-shaped void portion in which constituent members of the switch are assembled, and made of a synthetic resin material that is suitable for molding process and insulation. Moreover, when the switch constituent parts are attached to the housing, the attaching process is easily carried out through the opening section, that is, the opening on one surface of the concave shape. After the assembling process, the opening face of the housing is covered with a cover having a flat-plate shape, and easily closed into a sealed state.
The above-mentioned fixed contact member is easily formed by carrying out a punching process on a conductive plate. For example, the punching process is carried out so as to form an elongated small member that has a contact portion on one side with a wire connecting portion on the other side.
The above-mentioned movable contact member may be formed by bending a conductive plate spring member into a U shape. With respect to this member, for example, one end of the U-letter shape is placed on the contact portion side with the other end being placed on the operation force receiving face side. Moreover, another member having a partially different material may be used to form the contact portion and the spring portion, in an attempt to increase opening and closing currents or to provide a longer service life. For example, a material having high conductivity is used for the contact portion and a spring material having high elasticity is used for the spring portion, and the two parts may be joined into a U shape through a caulking process.
The above-mentioned operation member may be constituted by push-buttons and levers. Normally, the outer edge portion of the operation member is pressed by a restoring spring and allowed to stick outward from the housing, and held so as to be pressed without being pulled out, and when pressed down, it is guided so as to be inserted into the housing so that switching is made between contact portions. The operation member is also formed by a synthetic resin material suitable for molding process and insulation.
The above-mentioned contact portion may be integrally formed on the movable contact member and fixed contact member, or may be formed by attaching a conductive contact member.
The above-mentioned tilt-movement fulcrum portion is constituted by integrally forming a concave portion or a convex portion at an intermediate position on one member side of the movable contact member.
The above-mentioned contact switching mechanism may be formed by attaching a movable contact member to a plurality of fixed contact member placed in parallel with each other, in a see-saw fashion so as to freely tilt and move in a manner so as to face them in a direction orthogonal thereto. Thus, the movable contact member is reversed in a see-saw fashion by receiving the operational force of the operation member so that the contact portions between the movable contact member and the fixed contact member are switched.
In accordance with another embodiment of the present invention, since the contact switching mechanism has a seesaw structure for reversing the movable contact member in response to a switching operation, the movable contact member itself serves as a dual purpose part having the inherent contact function of the movable contact member and a restoring spring function so that it is possible to cut the number of parts and the number of assembling processes. Thus, the resulting simplified inner structure makes it possible to cut costs and save space, and consequently to miniaturize the device.
Upon assembling the device into the housing, a plurality of fixed contact members are placed in the housing in parallel with each other so that no wasteful layout space is required inside the housing and they are attached efficiently in a well-aligned manner. For example, in the case when three fixed contact members are assembled therein, these are aligned in three rows, and assembled compactly.
The movable contact member, in one embodiment, is formed into a U shape so as to have a small folded shape so that it is suitable for miniaturizing the device, and the two members, placed with the bent portion of the U shape serving as an apex, are allowed to elastically shift to provide sufficient elasticity so that it is possible to provide an appropriate spring function although it has a small size. Moreover, the movable contact member is placed face to face with the respective fixed contact members so as to contact therewith in a direction orthogonal to the aligned direction of the fixed contact members. Therefore, it is possible to provide an efficient layout arrangement in the same manner as an integral layout structure of the contact portion.
Furthermore, since the operation member is placed in contact with the outer face on the other member side of the U shape of the movable contact member in the length direction thereof, the operation member is allowed to contact the other member with a long length in the length direction thereof. Therefore, it becomes possible to obtain a sufficiently long operation length (operation stroke) of the operation member. In this manner, since it is possible to obtain the long operation stroke at the time of a switching operation, the device becomes less susceptible to adverse effects due to deviations in the attaching precision of the switch, when the switching area of the contacts is set within the range of the operation stroke. For this reason, it is possible to ensure on-off operations by eliminating the insufficient stroke, and it is also possible to prevent the switching parts from being damaged by accepting excessive strokes.
Moreover, upon switching the contacts, since the movable contact member itself is formed by a plate spring member that is bent in a U shape, and the plate spring member that has been bent is reversed energetically in a see-saw fashion in such a manner that the snapping action makes it possible to switch the contacts. Thus, it becomes possible to provide a quick switching operation, and consequently to prevent the generation of an arc between the contact portions. This arrangement makes it possible to provide a superior contact performance without the generation of an arc, and also to provide a stable switching operation with high reliability.
The supporting structure, which allows the above-mentioned movable contact member to reverse in a see-saw fashion, is arranged so that a concave portion is formed in one of a tilt-movement fulcrum on the movable contact member side and a fixed fulcrum on the common fixed terminal side for receiving this, with a convex portion being formed on the other fulcrum; thus, it is possible to obtain a stable tilt-moving function by using a simple structure.
Moreover, this contact switching mechanism has a simple structure in which the movable contact member is reversed in cooperation with a switching operation so that it is readily applicable to both of the push-button switch and the rotary-lever switch, and used as a highly versatile contact-switching mechanism.
In this aspect, one fixed contact member may be placed at a position opposing to one end of the movable contact member that is tilted to move in a see-saw fashion so as to carry out the switching operation, or a first fixed contact member and a second fixed contact member may be placed at positions opposing to two ends thereof so as to carry out the switching operation. In this case, since the two fixed contact members may have the same shape, the same parts may be commonly used.
Moreover, when an excessive tilt-movement regulating protrusion which prevents the movable contact member from making excessive tilt-movements is attached to the inner wall face of the housing on the fixed contact member side, the movable contact member that is tilted to move in a see-saw fashion is regulated so as not to be excessively tilted to move because of the excessive tilt-movement regulating function of the excessive tilt-movement regulating protrusion. Therefore, even when the contact parts on the unused side have been preliminarily omitted to form a space in the corresponding portion, the excessive tilt-movement regulating protrusion regulates the excessive tilt-movements of the movable contact member at the position of the space, thereby making it possible to maintain an appropriate tilt-movement state.
This excessive tilt-movement regulating protrusion is integrally formed on the inner wall face of the housing on the fixed contact member side so as to protrude toward the movable contact member side, and the amount of protrusion is designed so as to accept and receive the end of the movable contact member at a position retreated from the contact face position of the contact portion of the fixed contact member. Thus, it is maintained so as not to enter the reversing operation area of the movable contact member, and it becomes possible to ensure a stable reversing operation.
With this arrangement, the same housing can be commonly-used in all the switches of the single-pole double-throw switch and the single-pole single-throw switch having different contact structures. Moreover, the above-mentioned structure regulates the excessive tilt-movements of the movable contact member to prevent unstable movements such as positional deviations in the movable contact member; therefore, it is possible to appropriately maintain the balance of the contact structure, and consequently to maintain a stable switching operation. Thus, this arrangement makes it possible to omit a revising member such as a dummy contact, to obtain a stable contact performance by reducing the number of parts, and also to cut costs by commonly utilizing the housing.
When such a contact-switching mechanism is applied to, for example, a push-button switch, it is attached in such a manner that an external operation force is applied in the same direction as the advancing and retreating directions of the push button. Thus, in response to the advancing and retreating movements of the push button at this time, the U shaped movable contact member is elastically shifted so that the contacts between the movable contact member and the fixed contact member are elastically made in contact with and separated from each other so as to carry out a switching operation.
In the same manner, when such a contact-switching mechanism is applied to, for example, a rotary-lever switch, it is attached with such a pressure applying direction that with respect to the lever rotation direction, an external operation force is smoothly applied toward the rotation direction of the lever. For example, this is attached to the door of a refrigerator of double-sides opening type, the operation forces, applied when the door is opened and closed, are exerted virtually in parallel with the surface of the housing so that the lever, which protrudes from the surface of the housing, receives the operation force exerted in the surface direction, and is operated and switched with its one end being inserted into the housing while rotating on the rotation fulcrum.
In this case, the movable contact member having a U shape is elastically shifted in accordance with the rotation movement of the lever so that the switching operation is carried out with the contact portions between the movable contact member and the fixed contact members being elastically made in contact with and separated from each other.
Here, with respect to the movable contact member having a U shape, the opened end portion on the other member side is preferably bent inward into an elbowed shape so as to form an elbowed-shaped bent portion. This elbowed-shaped bent portion is designed so that, even when the operation force of the operation member, for example, a push-in force of the push button in the vertical direction, is exerted, the apex of the elbowed-shaped bent portion always serves as a contact point. Therefore, it is possible to provide a stable contacting force of the contacts in addition to the elastic function of the movable contact member having a U shape.
Moreover, with respect to the movable contact member having a U shape, a slide-contacting protrusion having a thin semi-circular shape, which protrudes in the length direction, is formed in the outer-surface center portion on the other member side, and the operation member is allowed to contact this slide-contacting protrusion in the length direction at the time of the operation. The formation of this slide-contacting protrusion provides not a face contact, but a point contact, at the time of slide-contacting the operation member when the switching operation is carried out. Therefore, the two members become less susceptible to mutual abrasions, thereby making it possible to provide a longer service life and smoother movements.